Reflector antennae are widely used in a variety of radiation transmission and reception applications. High efficiency, relatively low cost, potentially low weight, and broadband capability are but a few of the advantages offered by the reflector antenna. However, for most applications the precision of the surface of a reflector antenna is crucial to the antenna's ability to efficiently direct power from a source or to concentrate transmitted energy into a narrow beam.
The quality of a reflector antenna is determined by the gain obtained for a particular aperture size. The gain efficiency of the reflector is determined by the electrical field distribution across the antenna aperture. The field distribution in turn depends upon the excitation used to generate the field and the accuracy with which the reflector conforms to the ideal surface. Thus the more accurate the reflector surface, the more efficient the gain of the antenna.
Reflector antennae are not amenable to easy local phase adjustment, as is the case with a typical phase array antenna. Indeed, an antenna positioned in space is only capable of adjustment by very complex and costly means. While it is theoretically possible to periodically (or continuously) measure the surface of a reflector and correct its shape through the use of a mechanized means, the cost and complexity required are prohibitive. There is, therefore, a need for large reflector structures having a reflector surface possessed of a high degree of dimensional accuracy and stability.
One practical approach to constructing an accurate reflector surface is to provide a surface and associated support structure possessing sufficient stiffness and stability that no unacceptable surface distortions occur during the antenna's lifetime. While fabrication of a backing structure having sufficient stiffness to adequately maintain reflector shape is relatively easily accomplished, a complex arrangement of clips, bolts and fasteners is required to secure the reflector to the backing structure. Therefore, proper adjustment of the backing structure to the reflector is a laborious and time-consuming process.
Additionally, fabrication of a reflector backing structure requires that the structure conform very accurately to the reflector back surface to avoid causing distortions in the reflector front surface and thereby reduce gain efficiency. Reflector backing structures must, therefore, be individually designed to each reflector shape in order to insure a distortion free reflector surface. Because backing structures commonly employ rib-type trusses to provide support to the reflector surface, the shape of each rib must be redesigned for each individual reflector surface configuration. For large structures with complex reflector surfaces, the redesign of the backing structure becomes a very costly and time consuming engineering task.